[01/14] osdep: Add qemu_lock_fd and qemu_unlock_fd

They are wrappers of POSIX fcntl "file private locking".

Signed-off-by: Fam Zheng <famz@redhat.com>
---
 include/qemu/osdep.h |  2 ++
 util/osdep.c         | 29 +++++++++++++++++++++++++++++
 2 files changed, 31 insertions(+)

On 31.10.2016 16:38, Fam Zheng wrote:
> They are wrappers of POSIX fcntl "file private locking".
> 
> Signed-off-by: Fam Zheng <famz@redhat.com>
> ---
>  include/qemu/osdep.h |  2 ++
>  util/osdep.c         | 29 +++++++++++++++++++++++++++++
>  2 files changed, 31 insertions(+)
> 
> diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
> index 0e3c330..f15e122 100644
> --- a/include/qemu/osdep.h
> +++ b/include/qemu/osdep.h
> @@ -294,6 +294,8 @@ int qemu_close(int fd);
>  #ifndef _WIN32
>  int qemu_dup(int fd);
>  #endif
> +int qemu_lock_fd(int fd, int64_t start, int64_t len, bool exclusive);
> +int qemu_unlock_fd(int fd, int64_t start, int64_t len);
>  
>  #if defined(__HAIKU__) && defined(__i386__)
>  #define FMT_pid "%ld"
> diff --git a/util/osdep.c b/util/osdep.c
> index 06fb1cf..b85a490 100644
> --- a/util/osdep.c
> +++ b/util/osdep.c
> @@ -140,6 +140,35 @@ static int qemu_parse_fdset(const char *param)
>  {
>      return qemu_parse_fd(param);
>  }
> +
> +static int qemu_lock_fcntl(int fd, int64_t start, int64_t len, int fl_type)
> +{
> +#ifdef F_OFD_SETLK
> +    int ret;
> +    struct flock fl = {
> +        .l_whence = SEEK_SET,
> +        .l_start  = start,
> +        .l_len    = len,
> +        .l_type   = fl_type,
> +    };
> +    do {
> +        ret = fcntl(fd, F_OFD_SETLK, &fl);
> +    } while (ret == -1 && errno == EINTR);

As I've asked in the last version: Can EINTR happen at all? My man page
tells me it's possible only with F(_OFD)_SETLKW.

Max

> +    return ret == -1 ? -errno : 0;
> +#else
> +    return -ENOTSUP;
> +#endif
> +}
> +
> +int qemu_lock_fd(int fd, int64_t start, int64_t len, bool exclusive)
> +{
> +    return qemu_lock_fcntl(fd, start, len, exclusive ? F_WRLCK : F_RDLCK);
> +}
> +
> +int qemu_unlock_fd(int fd, int64_t start, int64_t len)
> +{
> +    return qemu_lock_fcntl(fd, start, len, F_UNLCK);
> +}
>  #endif
>  
>  /*
>

On Fri, 12/02 01:30, Max Reitz wrote:
> On 31.10.2016 16:38, Fam Zheng wrote:
> > They are wrappers of POSIX fcntl "file private locking".
> > 
> > Signed-off-by: Fam Zheng <famz@redhat.com>
> > ---
> >  include/qemu/osdep.h |  2 ++
> >  util/osdep.c         | 29 +++++++++++++++++++++++++++++
> >  2 files changed, 31 insertions(+)
> > 
> > diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
> > index 0e3c330..f15e122 100644
> > --- a/include/qemu/osdep.h
> > +++ b/include/qemu/osdep.h
> > @@ -294,6 +294,8 @@ int qemu_close(int fd);
> >  #ifndef _WIN32
> >  int qemu_dup(int fd);
> >  #endif
> > +int qemu_lock_fd(int fd, int64_t start, int64_t len, bool exclusive);
> > +int qemu_unlock_fd(int fd, int64_t start, int64_t len);
> >  
> >  #if defined(__HAIKU__) && defined(__i386__)
> >  #define FMT_pid "%ld"
> > diff --git a/util/osdep.c b/util/osdep.c
> > index 06fb1cf..b85a490 100644
> > --- a/util/osdep.c
> > +++ b/util/osdep.c
> > @@ -140,6 +140,35 @@ static int qemu_parse_fdset(const char *param)
> >  {
> >      return qemu_parse_fd(param);
> >  }
> > +
> > +static int qemu_lock_fcntl(int fd, int64_t start, int64_t len, int fl_type)
> > +{
> > +#ifdef F_OFD_SETLK
> > +    int ret;
> > +    struct flock fl = {
> > +        .l_whence = SEEK_SET,
> > +        .l_start  = start,
> > +        .l_len    = len,
> > +        .l_type   = fl_type,
> > +    };
> > +    do {
> > +        ret = fcntl(fd, F_OFD_SETLK, &fl);
> > +    } while (ret == -1 && errno == EINTR);
> 
> As I've asked in the last version: Can EINTR happen at all? My man page
> tells me it's possible only with F(_OFD)_SETLKW.

I think you are right, let's drop the condition.

Fam

> 
> Max
> 
> > +    return ret == -1 ? -errno : 0;
> > +#else
> > +    return -ENOTSUP;
> > +#endif
> > +}
> > +
> > +int qemu_lock_fd(int fd, int64_t start, int64_t len, bool exclusive)
> > +{
> > +    return qemu_lock_fcntl(fd, start, len, exclusive ? F_WRLCK : F_RDLCK);
> > +}
> > +
> > +int qemu_unlock_fd(int fd, int64_t start, int64_t len)
> > +{
> > +    return qemu_lock_fcntl(fd, start, len, F_UNLCK);
> > +}
> >  #endif
> >  
> >  /*
> > 
> 
>